Concentrating process and apparatus

ABSTRACT

The present invention generally relates to an improved process and apparatus for concentrating fluids. The process and apparatus have particular application for removing moisture from liquids containing entrained solids or solids in solution, such as liquid foods and the like. In the process, fluid is concentrated by atomizing it into fine droplet form, injecting the atomized droplets into a band of dry high temperature gas, preferably air, passing into a concentrating zone, subjecting the droplets to controlled shear and turbulence and collecting and withdrawing the concentrated fluid. The conditions for atomizing, injecting and concentrating are controlled to provide a figure of merit of at least about 30 where the figure of merit is defined as follows:

United States Patent [72] Inventors David D Peebles, deceased late of Davis, Calll. (by Margaret M. Peebles, Pebble Beach, Calif., Lois P. Meade, Appleton, Wisc., and James R. Bancroft, San Francisco, Calif., executors); Wayne E. Henry, Downers Grove, Ill. [2!] Appl. No. 740,429 [22] Filed June 13, 1968 [45] Patented July 13, 1971 [73] Assignee Carnation Company Los Angeles, Calif.

[54] CONCENTRATING PROCESS AND APPARATUS 11 Claims, 6 Drawing Figs.

[52] U.S. Cl. 159/4, 159/48 [51] Int-Cl. B0ld 1/16 [50] FieldotSeareh 159/4 8,4 13, 48

[56] References Cited UNITED STATES PATENTS 1,984,381 12/1934 Pebbles 159/4 S 2,119,932 6/1938 Stam 159/48 2,268,871 lll942 Hall 159/4 F 2,670,036 2/1954 Spalding 159/4 S 3.112.239 11/1963 Andermatt h 159/4 B 3,233,655 2/1966 Graham [59/41 1,364,403 l/l92l Muller 159/48 FOREIGN PATENTS 666,341 2/1952 Great Britain 159/4 S 530,613 12/1940 Great Britain 159/41 Primary Examiner-Norman Yudkoff Assistant E.raminer.l. Sofer Attorney-Eugene C. Ziehm ABSTRACT: The present invention generally relates to an improved process and apparatus for concentrating fluids. The process and apparatus have particular application for removing moisture from liquids containing entrained solids or solids in solution, such as liquid foods and the like. In the process, fluid is concentrated by atomizing it into fine droplet form, injecting the atomized droplets into a band of dry high temperature gas, preferably air, passing into a concentrating zone, subjecting the droplets to controlled shear and turbulence and collecting and withdrawing the concentrated fluid. The conditions for atomizing, injecting and concentrating are controlled to provide a figure of merit of at least about 30 where the figure of merit is defined as follows:

29:2 Sine 0 54 Tl/RATED AIR mom .a 22

FAN

29 TDCYCLHNE 4 4 FfiD INSULATION 2'7 PATENIED JULY 3 I971 3' 592 I 253 sum 3 or 3 By MARE/41717 M. P558153, LOIS I. 445726 AND JAMES R. BAA/(ROFL EXCUTOR S.

WA Y/Vf f. HENRY AQT'TOQME v CONCENTRATING PROCESS AND APPARATUS The apparatus of the invention includes a concentrating chamber, gas inlet means adapted to deliver gas at high velocity into the chamber, means for atomizing fluid disposed adjacent said gas inlet means and adapted to inject atomized droplets into gas passing to said chamber, means for supplying fluid to said atomizing means, means adapted to provide a zone of controlled turbulence in the chamber, means for removing gas from the chamber and means for withdrawing concentrated fluid from said chamber. In one embodiment of the invention, a plurality of air inlet and atomizing means are positioned so as to introduce said droplets into a plurality of inlet air streams which converge in said chamber to provide a zone of turbulence within said chamber.

Obviously, it would be of considerable importance to be able to provide a more efi'icient and economical process and apparatus for concentrating fluids such as liquid foods containing dissolved or dispersed solids which would not exhibit any tendency to adversely affect the fluid (e.g. contaminatinga sterile fluid, initiating heat degeneration or nutritional depreciation of constituents of the fluid, etc.).

Accordingly, it is a principal object of the present invention to provide an efficient multipurpose process for concentrating sterile and nonsterile fluids to a desired degree rapidly, economically and without degradation of the fluid.

It is a further object of the present invention to provide an improved process of concentrating liquid foods containing entrained, dispersed or dissolved solids while preserving desirable characteristics of the solids, and for recovering efficiently the concentrated liquid and/or solids.

It is also an object of the present invention to provide an improved apparatus which operates with a high degree of efficiency for concentrating fluids such as, for example, liquid foods and the like, which apparatus is relatively simple, operates throughout a wide temperature range and is relatively inexpensive.

It is yet another object to provide apparatus capable of operating as a fluid concentrator or evaporator, with a lower power input per unit of fluid evaporated, and which can be used with a wide variety of feed fluids.

Further objects and advantages of the present invention will be apparent from a study of the following detailed description and the accompanying drawings, of which are:

FIG. I is a vertical section through the center of a preferred embodiment of the apparatus of the invention, particularly illustrating the arrangement of the feed and air inputs with respect to the chamber of the device;

FIG. 2 is a detailed vertical partial section through an atomizing head, gas inlet means and liquid feed means of the embodiment of FIG. 1;

FIG. 3 is a front view of the atomizing head of FIG. 2 partially broken away to expose the atomizing path in said head;

FIG. 4 is a side elevation partly broken away of a second embodiment of the apparatus of the present invention;

FIG. 5 is a top plan view, partly broken away, of the atomizer and gas inlet shown in FIG. 4;

FIG. 6 is an enlarged partial vertical section through the atomizing head and gas inlet means illustrated in FIGS. 4 and 5.

The present invention includes a process generally as described above, which process atomizes a concentratable fluid, which may contain, if desired, entrained, dissolved or dispersed solids or the like, into controlled fine droplet size and which concentrates the droplets rapidly and economically to a substantial extent. The process maximizes the heat transfer rate between the droplets and a stream of dry high temperature gas as the stream passes to and while it is within a concentrating zone, by employing controlled turbulence and shear. The operating conditions necessary to effect the desired result are reflected by a figure of merit which is in excess of about 30, the figure of merit being defined as follows:

" 2 1 1) i i) Sine 0 4 n Figure of merit 74X 10 W AHV where:

74X 10 is a constant 1r is 3.1415

G is mass velocity of gas in gas band in lb. of dry air/min. I 1b I sq. ft. X 10 m, is viscosity of gas at inlet temperature in gas band T is temperature F.) of gas at inlet to concentrating zone T,, is wet bulb temperature F.) of gas at inlet to concentrating zone AHv is heat of vaporization in B.t.u./lb.

W is the width of gas band atinlet in inches 0.4 is a constant T ifs radius of rotor atomizer (atomizing means) in eet I is mass velocity in lb./min./ft. of \vetted periphcry of atomizing means [i is viscosity of fluid at inlet fluid temperature in lb. sec./sq. ft.

m, is density of 1b. /cu. ft.

a is surface tension of fluid at inlet fluid temperature fluid at inlet fluid temperature in N is speed in r.p.m. of atomizer (atomizing means) L is Wetted periphery of atomizer (atomizing means) in feet 0 is the angle of entry of droplets into the gas band tease The apparatus of the present invention employs one or a plurality of 'atomizers whichproject fluid, preferably liquid, in the form of finely divided droplets of controlled size at a controlled rate of speed and injection angle into a rapidly moving band or stream of heated dry gas, preferably air. A plurality of such atomizers and streams of gas maybe employed. The airstream(s) pass(es-) into the concentrating chamber by means of inwardly directed channels and is subjected to turbulence therein. Means are provided adjacent opposite ends of the chamber for exhausting air or other'gaseous heat. transfer medium and concentrated fluid, respectively, from the chamber.

Now referring more particularly to the present process, any fluid, particularly liquid, whether or not it contains entrained, dispersed or dissolved solids, can be concentrated by the present process. The process features a high throughput rate, a high degree of evaporation per unit time, and complete protection of the fluid being concentrated, despite the use of heat transfer media having high temperatures. No appreciable degradation, scorching, flavor or nutritional loss occurs'when the process is employed on foods. Foods which heretofore have been incapable of being economically and/or substantially concentrated by mechanical means can be readily and. effectively treated, for example, egg whites. Various types of heat sensitive liquid products are suitable as feed liquids forthe process. Excellent results are obtained with liquids such as dairy products, including whole milk, skim milk, whey, and other foods such as fruit juices, vegetable juices, meat juices, fl'sh extracts. and the like.

In carrying out the present process, fluid is passed to and atomized in a suitable atomizing zone. The atomized fluid is in fine droplet form, the exact applicable average diameterrange varying with the viscosity of the fluid and other factors. The atomizing can-be accomplished by any suitablemeans, for example, a rotary atomizer of conventional type. The atomizer projects the droplets into a rapidly moving band of high temperature gas which serves as the heat transfer medium and which passes into a concentrating zone. When such an atomizer is .employed to form and project the fluid in fine droplet forminto the rapidly moving band at a selected angle, a tip speed of from about 25,000 to in excess of about 35,000

feet per minute for the atomizer is usually employed. It is necessary to impart. in particular. high velocity to the droplets in order to assure adequate formation of the heat transfer film of extremely small thickness. Any angle of entry of the droplets into the air band can be employed. However, maximum shear is obtained when the angle of entry is 90 with respect to the stream.

Although air is preferred, other gaseous heat transfer media such as heliumQnitrogen and the like can be employed. The heat transfer medium is, as indicated, in the form of a band of sufficient width to prevent the droplets from penetrating from one side thereof through the opposite side, when considered with the velocity of the band. The mass velocity is usually in excess of about 1,0001bs./minute, where the width of the band is less than about inches. Such band is usually less than about 5 inches. The band temperature at the inlet to the concentrating zone is usually about 4001,000 F. or more, high temperatures generally being most suitable.

The droplet size is controlled by regulating the tip speed and other parameters of the atomizer. The angle of injection of the droplets so formed into the gaseous band is such as to foster high shear, while turbulence is efiected in the concentrating zone to maximize the extent and rate of heat transfer between the heat transfer medium and the droplets. This concentrates the droplets most efficiently.

It is important that parameters are applied which simultaneously maximize both the rate and the extend of evaporation. 1n carrying out the process, within practical limits, the surface area of the fluid to be concentrated is initially very large by producing the droplets in as small an average diameter as is practical, with respect to energy requirements and feed throughput. The rate of heat transfer in the system is increased by controlling the temperature of the heat transfer medium and the angle of entry of the liquid into the heat transfer stream. Thus, the shear force exerted on the droplets by the stream is such as to smear the droplets, i.e. increase further the surface area of the droplets, so that the heat transfer which ensues is essentially very thin film heat transfer. Turbulent mixing of the droplets with the stream in the concentrating zone assures optimum contact of the liquid of the droplets with unsaturated heat transfer medium. In the latter regard, the resistance to transfer of heat under the prevailing thin film conditions is reduced by employing very high localized turbulence in the concentrating zone, as defined by Reynolds Numbers, cross-vectors of fluid flow around the -individually suspended droplets maximizing the desired heat transfer contact. The turbulence can beefi'ected in any number of ways, as by intersecting the gas band with itself, or two gas bands with each other, or by providing a baffle system, etc.

It has been found that the figure of merit characterizing the described conditions should be above about 30 and preferably should be above about 50 in order to assure a commercially practical process. Conventional evaporating systems employ conditions which generate figures of merit usually well below 30, and, accordingly, exhibiting a relatively high degree of inefficiency of operation. In the most efficient conventional evaporators, such as the swept film evaporator, a high surface to volume relationship is maintained for the fluid to be evaporated, but the gas flow, i.e. the rate of flow of the heat transfer medium through the system, is so low that the medium is essentially saturated. This seriously impedes the rate of evaporation and also the extend of evaporation. Accordingly, alow figure of merit results, which reflects the inefficiency of um, high flow rates for the heat transfer medium and high shear and turbulence, all without deteriorating the chemical or physical nature of the concentrated material. The temperature and volume of input gas (heat transfer medium) on the one hand and the composition, viscosity and rate of feed fluid input on the other hand are balanced to maintain a desirably low difference between the measured wet bulb and the theoretical wet bulb temperatures of the system. The droplet size and injection speed are also correlated for this purpose. The net result is a highly efficient, economical process, capable of concentrating various types of fluids, all with equal ease and rapidity, and without adversely affecting the same. Moreover, some liquids can be concentrated by the present process to a greater extent than by existing conventional concentrating procedures.

The following are examples of the present method:

EXAMPLE I An apparatus for condensing tomato juice of conventional solids concentration (26 wt. percent) was employed which included an-atomizing rotor, the arc of which was 12 inches in diameter and the speed of rotation of which during operation was 12,000 r.p.m. A rapidly moving band of dry air having a temperature of 596 F. was passed into a concentrating chamber in the form of a cyclone at the rate of 1,095 lbs. per minute, with the band having a width of 3.75 inches. The rotor was positioned so as to inject the tomato juice in fine droplet form directly into this band of hot air at the rate of 16.5 gallons per minute when the rotor was rotated at 12,000 r.p.m. During operation of the system, the wet bulb temperature was F. (the temperature of the air at the point of withdrawal from the evaporating chamber). The system was operated by rotating the atomizer at the indicated speed and feeding the tomato juice therefrom at the indicated rate into the hot dry air passing into the chamber. The remaining conditions for the system were balanced, including turbulence and shear. A zone of turbulence was formed in the chamber by converging the indicated band in a concentrating zone with an identical band having the same temperature-and containing a like concentration of the tomato juice injected at the same rate. A figure of merit of 79 was obtained as follows:

In calculating the figure of merit, the parameters were as follows:

Figure of merit=79 AHV sine 0 Substituting in the equations 43 21 Figure of mer1t-74X 10 W Mb Substituting in the first equation Figure of merit 74 X 10 1). l (7.2X10- (1095) "-(Qti- 12A) Figure of merit =70 'A volume concentration of 2.64 times was obtained at the high throughput indicated, with only a 1 F. difference between the theoretical and actual wet bulbs, clearly indicating a high efficiency of operation. Of considerable importance, no deterioration in the flavor, odor, appearance, taste or nutritive value of the tomato juice occurred, so that the concentrated product was of uniformly high quality, despite the high temperature of the air inlet stream into which the tomato juice was injected.

EXAMPLE ll fnalulaiiitgthEhflr of rhritfth situates were as folws Defining parameters per rotor-band combination W== 4 inches G= 1120 lbs. of dry air/min. #b=40-2X 10 r= .585 feet 1=41.5 lbs./min./ft. of wetted periphery 2.45X 10" 61.52 a=9.6X 10 N 12,000 L 3.70 sine 0= 1 As before, substituting for in the equations s-D D g) T, T,) Figure of merit 74 10 Fb AHV s1ne0 EXAMPLE m A system essentially the same as that set forth in example 1 was employed to concentrate whey for use as an animal feed supplement. However, the system employed the following conditions:

Conditions:

Using 12-inch diameter rotors, the parameters for each rotor-band combination were:

3,000 r.p.m.

400 F. inlet air temperature 20 gaL/min. feed 500 lbs. of dry air/min.

5 inch air band F. wet bulb.

Operation of the system was calculated to provide a figure of merit of 24, which was obtained as follows:

41D? e rn) Figure of ment-24-74X10 W m, AH

Sine 0 In calculating the figure of merit, the following parameters were employed:

Definigglgparameters per rotor-band combination 7! W: 5 inches. G: 500 lbs. of dry air/min. u 40.2X 10 T,= 400 F. T,= 130 AH,= 1200 r= .5 feet I=62.8 lbs. /min./ft.of wetted periphery 2.45 X 10- p 61.25 o'= 9.6x 10' N= 3000 Lw= 3.14 sine 0= 1 Substituting in the equations as before, figure of merit= 24.

A volume to volume concentration ratio of 1.221 was obtained and the system exhibited a 25 F. difference between theoretical and actualwet bulb. Although the whey concentrate was not depreciated in chemical or physical characteristics, the extent of concentration was so low as to be inefficient and relatively useless for commercial purposes.

A relatively small-difference between theoretical and actual wet bulb indicates a high degree of utilization of heat energy put into the system, i.e. efficiency of the system since the purpose of that energy is to'cause evaporation and the extent of the evaporation is reflected by how close the actual wet bulb reading approaches the theoretical value. However, in order for the system to be worth employing, it must also evaporate to reasonably high concentration of the feed at a relatively high feed rate.

Example 1 clearly indicates a minimal difference between theoretical and actual wet bulb while simultaneously obtaining.v a high concentration at a high feed rate'so that the system was in all respects operatingefliciently. Example 11 illustrates that a lower figure'of merit, still satisfactory, reflects lowered efficiency, in this instance a relatively large difference between theoretical and actual wet bulb, but with-a relatively high concentration ratio at a high flow rate. When the figure of-rnerit falls below 30, the system is so inefficient so as to be wholly unsatisfactory commercially, as-jnexample lll where'the concentration ratio'was almost nil. Although the flovrrate was" relatively high;v the difference between theoretical and actual wet bulb. temperatures was very large. On the basis of these and similarresults, it has been determined that the' figure of merit must be at least about 30 in order to represent a sufficiently high-degree of efficiency utilizing the present-methodto commercially employ the same.

It will be'understood that the present process'has a wide variety of applications and can be carried inany suitable.ap.-

paratus capable of establishing and maintaining the parame Mu-W1 .i....... a Mu-1m m nhtain'a-fiflure' ofrn'erit.-.

of at least about 30. One such form of apparatus is as more described hereinafter, which apparatus can also be usefully employed in operations beyond the limits of the present process.

Now referring more particularly to FIG. 1, a preferred em bodiment of the apparatus of the invention is shown in cross section. Fluid to be concentrated enters a chamber 11 through a conduit 12. The chamber 11, conduit 12 and other parts of the system contacting liquid or saturated gas preferably are constructed of a rust resistant material, such as aluminum or stainless steel. Conduit 12 is rotatably mounted within casing 13. A motor (not shown) drives conduit 12 and a rotary atomizing head 14 attached to the opposite end of conduit 12. Liquid enters the center of the centrifugal atomizing head 14 from conduit 12 and is dispersed radially by the centrifugal force of the rotating head 14. A series of meshing ridges and valleys generally designated as 16 in the atomizing head 14 form a tortuous path which distributes the liquid as a thin film which passes radially outwardly from the center of the rotating head 14. This thin filrn of liquid is atomized when projected from periphery (FIG. 2) of the atomizing head 14 at high tip velocity.

Air or other gas enters the chamber 11 through inlet 17 as a band. The gas band is at elevated temperatures which may range from about 300 F. to 1,000" F. or more, preferably about 400l,000 F. lnlet 17 connects with a plenum l8, and the plenum 18 is supplied with hot gas through a conduit 19, which in turn receives hot air from a fan 21 and a heat exchanger 22.

In the embodiment of FIG. 1, the gas passing through inlet 17 forms a band which impinges at an angle to the plane of rotation of the atomizing head 14. The outside wall of the air inlet 17 may be adjusted to vary the width of the air inlet 17. In this manner, the effective width A" (FIG. 2) of the air band impinging across the atomizer may be increased or decreased. The gas band passes through inlet 17 towards the center 23 of the chamber 11 for convergance with a like band or stream from the opposite side of the chamber 11 to provide desired turbulent mixing. Alternatively, an arrangement (not shown) can be provided for causing the stream to contact another turbulence-forming means, for example, a baffle system (not shown).

Parts of chamber 11 or feed conduit 12 in contact with plenum 18 or inlet 17 are cooled or insulated from the high temperatures in the plenum 18. Thus, a passage 24 insulates the chamber 11 from the plenum l8. Insulation in an area designated 27 in FIG. 1 further protects the feed conduit 12 and atomizer 14 from the high temperatures of the plenum 18, which may be as high as 1,200 F. and usually is about 500 l,000 F.

The opening in the plenum side of inlet 17 preferably has a smaller cross-sectional area than the chamber side. The restriction at the plenum side of inlet 17 causes a slight back pressure in plenum chamber 18, and air is distributed more uniformly around the entire circumference of inlet 17.

As will be explained later, the atomized droplets of liquid are projected from the atomizing head 14 into the band of hot air or other gas passing through inlet 17. It will be understood that where reference is made to air, another gas can be used. Preferably, a major portion of the atomized, partially concentrated particles of liquid are carried in the air band into a zone of turbulence 23 created in the center of the chamber 1 1. This is preferably achieved by controlling the width of the air band, tip speed of the atomizing head 14 and air volume so that liquid particles will not be projected through the band of air before sufficient water is removed and neither will they be over-dried or burned in the hot air band.

After contacting the hot air, a portion of the liquid concentrate loses velocity, falls by gravity and is collected in the bottom of the chamber 11 and withdrawn through a valve 28 by a discharge pump (not shown). Saturated or partially saturated air is exhausted at an opening 29 in chamber 11 to a cyclone (not shown) or another type of air liquid separating unit to remove entrained liquid from the air. Liquid removed by the cyclone can be recycled if further concentration is desired.

A second, substantially opposed, atomizing head 33 substantially identical to head 14 can be provided, as shown in FIG 1, along with an air inlet 34 of the same construction and function as described above for inlet 17 and atomizing head 14 A conduit 31, similar to conduit 12, supplies liquid to the atomizing head 33, and acts as a shaft for rotating atomizing head 33. The conduit 31 is enclosed in a casing 32. Air enters the chamber 11 through inlet 34 from a plenum 36. The plenum 36 issupplied with hot, dry air by a conduit 37 connecting the plenum 36 with the heat exchanger 22.

FIG. 2 is a partial section through the air inlet 17 and the right side of the chamber 11. The view illustrates in detail the construction of the atomizer l4, liquid feed input system 12 and 13 and air inlet systems. Conduit 12 is housed in a casing 13 and supported by a bearing 15. The bearing 15 is oil cooled through a gland 35 surrounding it and supplied by tubes 8 and 9. The bearing housing is supported by a plate 10 which is fastened to atomizer housing 7 and 6, the latter being water cooled through a conduit 5.

The rapid mixing of liquid feed and hot dry air (or other gas) in the operation of the apparatus of this invention achieves a small, stable Ar between the wet bulb and dry bulb temperature at the outlet 29 for high rates of concentration. Data demonstrating this advantage, along with specific product examples are set forth in table I.

An atomizer head speed of above about 10,000 rpm. with a 10-inch diameter atomizer (about 26,000 feet per minute tip speed) is suitable for obtaining efficient concentration of most liquids. Advantageously, an atomizer speed of above about. 12,000 r.p.m. with a 10-inch diameter atomizer is used to obtain more efficient concentration. It is preferable that a tip speed as high as 35,000 feet per minute or more be used. The preferred range of tip speeds can be achieved with a 12-inch atomizer at about 1 1,000 rpm. A minimum atomizer speed of about 6,000 rpm. is preferable to provide centrifugal force of atomization. This operating range assumes no slippage between the liquid particles and the atomizer tip. Thus, the initial velocity of the atomized particle would be approximately equal to the atomizer tip speed.

The air band around the atomizer 14 is advantageously less than about l2inches across (dimension A, FIG. 2). The effective width A of the air band or donut" of air may be varied by changing the position of the air inlet wall 25 or by changing the angle of divergence of the air inlet wall 25.

The preferred effective width A" of the air band is from about 1% inch to about 7 inches with an atomizer diameter of 10 to 20 inches. In general, it has been found that a narrow air band width increases the efficiency of concentration. The minimum width of the air band, in practice, is limited by the back pressure required to force hot air from the plenum 18 to the air inlet 17.

The temperature, air input volume through inlets l7 and 34 of FIG. 1 to the chamber 11 and the liquid feed input volume are correlated to achieve the highest rate of concentration with a minimum difference between the wet bulb and dry bulb temperatures at outlet 29 within the concentrating chamber. If the At between the wet bulb and dry bulb at outlet 29 becomes excessive, part of the feed will be dried or burned rather than concentrated. It is, thus, desirable to maintain the balance between the rate of liquid feed input through the atomizer and hot air input to the chamber through the air inletso as to stabilize the At between the wet bulb and dry bulb temperatures at outlet 29 at a value of less than 30 F.

Preferably, the At within the chamber 11 is maintained below about 20 F.

In each of the product examples set forth in table I, both atomizers were inoperation simultaneously. The operating conditions, atomizer rpm. and air inlet volume are set forth in Columns 1-7 of table I. The last two columns of table I give the initial total solids content of the liquid feed and the concentration achieved in the chamber. Unless otherwise indicated, the concentration was achieved on a single pass, without recycling.

TAB LE 1 Air Rotor volume Air number Initial Cone Size Speed band Temp. dry air Feed Temp. tensile (volume Product (inches) \r.p.m l (inches F. (min.) (g.p.m.) F.) strength 6 ratio) Whey. 10 1.. 000 7 748 828 24 2 7. 5 1. 6 10 14, 000 3. 4 756 741 17 2 6 2. 84 12 12.000 6 447 1, 614 23 4 6. 47 l. 79 503 1, 213 17 2 13. 65 2. 04 21 pass 616 S30 14 2 6. 2. 50 758 763 22 2. 6 2. 00 l2 12, 000 3. 75 752 760 16 2. 0 7 2. 50 D0 2.44 753 683 16.0 6.0 26 1.96 2. 44 757 664 12. 0 2. 5 6 3. 25 754 871 24. 0 3. 5 6 2. 00 2. 75 760 757 16. 0 2. 5 7 2. 28 14 12, 000 5. 00 752 757 13. 0 2. 0 7 3. 64 2. 75 753 715 14. 0 13. 0 26. 75 1. 61 D0 2. 75 752 688 ll. 0 2. 0 7 83 1. 44 747 686 10. 5 2. 0 6. 5 4. 08 omato 12 12,000 5 684 830 11 3 6. 0 2. 50 2d 428 1, 164 18. 3 4 11. 0 1. 86 392 1, 188 21. 0 22. 0 1. 36 596 1, 095 16. 5 l 5. 5 2. 64 720 1, 070 16. 0 16. 0 6. 7 4. 60 726 806 14 0 10 2.6 692 800 11 2 6 4. 33 725 862 2, 9 3. 44 695 924 20. 5 3. 0 7. 8 4. 19 596 887 13 10 11. 8 3. 45 641 898 20. 0 2. 7 12. 71 2. 78 559 1, 120 19. 1 24 15. 46 1. 90 687 1, 107 20. 8 18. 5 8. 81 2. 92 395 1, 084 10. 8 1. 0 11. 79 -2. 21 664 1, 020 16. 5 3. 0 14. 04 3. 09 421 1, 132 15. 5 5. 0 43. 46 1. 77 714 1, 063 18. 0 3. O 32. 05 2. 44

a Measured as it enters the chamber through the air inlet 17 or 34.

b Air volume is in pounds of dry air per minute entering the chamber.

0 A1 with the dry bulb measured in the riser 29. 9 Initial total solids content of the liquid feed.

A synergisticlike effect has been discovered between the multiple atgn izers and air inlets. To illustrate this effect, the atomizer and air inlet on one side of the apparatus were blocked off and the apparatus was operated using only one atomizer and air inlet This procedure was then repeated blocking off the opposite atomizer and air inlet. The runs were then repeated using both atomizers and air inlets. It would be expected that the use of two atomizers would be merely twice as effective as one rotor. However, table ll demonstrates that a feed of 16 gallons per minute is required to obtain a A! of approximately 2 F. between the wet bulb and dry bulb with a 2 to 1 concentration using either atomizer independently. When both atomizers were operating simultaneously, it required only 19.5 gallons per minute (rather than 32 gallons per minute) to maintain approximately 2 F. Ar and obtain a concentration of 2.5 to 1. With a 8 F. At, it required l0 gallons per minute feed to obtain a 3.5 to 1 concentration using asingle atomizer. It required only 13 gallons per minute (rather than gallons per minute) feed under identical conditions to obtain a higher 4.5 to 1 concentration when both atomizers were operating simultaneously. The simultaneous operation of a plurality of atomizers in the manner described herein gives concentration of liquids not obtainable with asingle rotor and air inlet system. In all instances, the rotor speed was 12,000 r.p.m., the air band width was constant in all runs and the rotor size was 14 inches.

directly with the cyclone 70, so that the flow of heated air bearing the atomized liquid and entering the cyclone 70 creates a swirling zone of turbulence within the cyclone 70 to facilitate heat transfer between the atomized liquid and the heated air. Thus, the band of air in the cyclone intersects itself and thereby acts as if it were a band converging on a separate second band to establish the turbulent mixing desired. The turbulence created is similar to that produced by opposed atomizing heads and air inlets, and serves the purpose of maximizing mixing of the droplets with unsaturated gas from the gas band, assuring the most rapid type of concentrating.

In this second embodiment, the cyclone 70 is of commercial design, for example, the type commonly used to separate entrained liquid from an airstream.

As shown in FIG. 4, channel 53 encloses the atomizer'Sl and the air inlets 52 are positioned about the periphery of the atomizer 51 so that a band or donut" of air moving at high speed toward the cyclone passes around the atomizer 51 at its periphery.

FIG. 3 is a partially exposed view of the face of the atomizer 51. The cutaway portion illustrates the irregular ridges and grooves which spread theliquid feed into a thin film as it passes radially from the center of the periphery 63 (FIG. 6) of the atomizer 51. The atomizer 5 l is supported by a housing 56 which contains a shaft 55 for rotating said head 51. A motor 54 drives the shaft 55 through a belt arrangement 59.

TABLE 11 Air volume number Vel. over Initial Rotor Temp. dry air] rotor Feed Temp. Cone. tensile No. F.) min (IL/min.) (g.p.m.) F.) (value) strength FIG. 4 illustrates an altemative embodiment of the inven- As shown in FIG. 6, shaft functions as a conduit for tion wherein an atomizer 51 is positioned in a tangent to a liquidfeed passing'to the atomizer 51. The crosshatched area cyclone 70. The objective of this embodiment is to obtain the benefits of a zone of maximum turbulence without resorting to opposed atomizers and gas inlets with. converging opposed gas bands to achieve the desired turbulence. An air inlet-52 emits a flow of hot air intoa channel 53 connected on a tangent within the heat shield 61 illustrates insulation protecting the atomizer 51 and the drive shaft bearing 57 from hot inlet air. The bearing 57 is' cooled by oil supplied by conduits Hand 72, and boththe bearing 57 and the shaft 55 are further protected by water cooled glands 73 supplied by tubes 58.

Hot dry air is fed to the air inlet 52 from a plenum (not shown) in the manner previously described Hot inlet air forms a defined band about the periphery of the atomixer 51 and the liquid feed is atomized and projected into the air band from the tip of the atomizer 51.

Contact of atomized particles of liquid with the flow of hot air from the inlet 52 removes water from the particles and entrains the particles in the flow of air. The partially concentrated liquid entrained in the airstream flows into the cyclone where it is subjected to extreme turbulence and the concentrate is collected from the bottom of the cyclone 50.

The present apparatus has the advantage of being relatively simple in construction, but capable of high speed operation over an extended period of time on a wide variety of liquid feeds. High temperatures are employed along with high throughput rates, and substantial concentration can be effected in less time and at a lowered operating cost than conventional commercial concentrators. The present apparatus is also capable of being used as a dryer, as a high speed mixer and for other related operations. lts atomizers can be of a form distinct from the described rotary atomizers, if desired, and it will be understood that one or a plurality of means can be employed to provide one or a plurality of inwardly directed high temperature bands of gaseous heat transfer medium. The apparatus, because of its design, can be effectively operated on sterile feed to keep that feed sterile throughout the concentrating procedure, whereby a sterile product can be obtained. This is of considerable importance in the processing of such types of liquids as certain liquid foods and other liquids readily degradable by microbial activity.

While the invention has been described with reference to particularly preferred embodiments, it will be appreciated that modifications of the preferred embodiments other than or in addition to those enumerated will occur to those skilled in the art upon reading the foregoing specification. Accordingly, it is intended that all those modifications which fall within the scope of the appended claims be included as part of the present invention.

Having described the invention, what we claim is:

l. A process for concentrating a fluid which comprises:

atomizing fluid into fine droplet form in an atomizing zone;

injecting the atomized droplets into a rapidly moving band of dry, high-temperature gas passing into a concentrating zone at an angle to said band of gas;

subjecting the atomized droplets in said concentrating zone to controlled shear and turbulence whereby the fluid is concentrated; and

collecting and withdrawing concentrated fluid from said concentrating zone;

the conditions for said atomizing, injecting and concentrating being controlled to provide a figure of merit of at least about 30, said figure of merit being defined as:

G is mass velocity of gas in gas band in lb. of dry air/min. pg, is viscosity of gas at inlet temperature in gas band in lb. min. 9 sq. ft. X 10 T. is temperature (F.) of gas at inlet to concentrating zone T, is wet bulb temperature (F.) of gas at inlet to concentrating zone AH, is heat of vaporization in B.t.u./lb.

W is the width of gas band at inlet in inches 0.4 is a, constant lb./cu. ft. 7 v i surface tension of fluid at inlet fluid temperature in lb. sq. X 1.6X 10 N is speed in r.p.m. of atomizer (atomizing means) L is wetted periphery of atomizer (atomizing means) in feet 0 is the angle of entry of droplets into the gas band in degrees 2. The process of claim 1 wherein the fluid being concentrated is milk.

3. The process of claim 1 wherein the fluid being concentrated is vegetable juice.

4. The process of claim 1 wherein the fluid being concentrated is fruit juice.

5. The process of claim 1 wherein the fluid to be concentrated is sterile and wherein said process is carried out aseptically to provide a sterile concentrated product.

6. The process of claim 1 wherein the inlet gas to the concentrating zone is air at a temperature of about 400 F.- l .000 F.

7. The process of claim 6 wherein the inlet air volume to the concentrating zone and its rate of feed, the size of said droplets and the shear and turbulence produced are correlated to maintain the figure of merit above about 50.

8. The process of claim 7 wherein the mass velocity of the dry air at the inlet to the concentrating zone is in excess of about 1,000 lbs. per minute and wherein the width of said band is less than about 5 inches.

9. The precess of claim 8 wherein said atomizing zone comprises a pair of substantially opposed, coaxial rotary atomizers disposed on opposite sides of a cyclone which comprises said concentrating zone and wherein a converging airstream is directed into said cyclone around the periphery of each of said atomizers at an angle to the plane of rotation of the atomizer to provide said controlled turbulence.

10. An apparatus for concentrating liquid feed which consists essentially of:

a concentrating chamber;

a revolving disc atomizing means associated with said concentrating chamber to atomize a liquid feed into fine droplet form;

gas inlet means positioned about the periphery of said atomizing means adapted to deliver an annular band of gas at high velocity into said chamber around the periphery of said atomizing means at an angle to the plane of said atomizing disc whereby said atomized liquid feed is peripherally and radially discharged from said atomizing disc into said bond of gas;

said gas inlet means being figured to deliver into said chamber said annular band of gas of sufficient thickness to prevent the atomized liquid feed from penetrating through said gas band and being positioned whereby said band of gas delivered into the chamber provides a zone of high turbulence in said chamber;

means for supplying said liquid feed to said atomizing means;

said atomizing means comprising 555;; of spaced, collinear, rotary atomizers positioned adjacent opposite sides of said chamber, and whose common axis is concentric with the axis of said gas inlet means, and said gas inlet means comprises a pair of converging, opposed frustocones with their small bases respectively positioned around the periphery of each of said atomizers to provide a pair of inwardly directed converging annular gas streams which impinge in said chamber to form a zone of turbulence;

means for exhausting gas from said chamber;

streams having a thickness of from about 1% inches to 7 inches at the periphery of said atomizer. 

1. A process for concentrating a fluid which comprises: atomizing fluid into fine droplet form in an atomizing zone; injecting the atomized droplets into a rapidly moving band of dry, high-temperature gas passing into a concentrating zone at an angle to said band of gas; subjecting the atomized droplets in said concentrating zone to controlled shear and turbulence whereby the fluid is concentrated; and collecting and withdrawing concentrated fluid from said concentrating zone; the conditions for said atomizing, injecting and concentrating being controlled to provide a figure of merit of at least about 30, said figure of merit being defined as:
 2. The process of claim 1 wherein the fluid being concentrated is milk.
 3. The process of claim 1 wherein the fluid being concentrated is vegetable juice.
 4. The process of claim 1 wherein the fluid being conCentrated is fruit juice.
 5. The process of claim 1 wherein the fluid to be concentrated is sterile and wherein said process is carried out aseptically to provide a sterile concentrated product.
 6. The process of claim 1 wherein the inlet gas to the concentrating zone is air at a temperature of about 400* F.-1, 000* F.
 7. The process of claim 6 wherein the inlet air volume to the concentrating zone and its rate of feed, the size of said droplets and the shear and turbulence produced are correlated to maintain the figure of merit above about
 50. 8. The process of claim 7 wherein the mass velocity of the dry air at the inlet to the concentrating zone is in excess of about 1,000 lbs. per minute and wherein the width of said band is less than about 5 inches.
 9. The precess of claim 8 wherein said atomizing zone comprises a pair of substantially opposed, coaxial rotary atomizers disposed on opposite sides of a cyclone which comprises said concentrating zone and wherein a converging airstream is directed into said cyclone around the periphery of each of said atomizers at an angle to the plane of rotation of the atomizer to provide said controlled turbulence.
 10. An apparatus for concentrating liquid feed which consists essentially of: a concentrating chamber; a revolving disc atomizing means associated with said concentrating chamber to atomize a liquid feed into fine droplet form; gas inlet means positioned about the periphery of said atomizing means adapted to deliver an annular band of gas at high velocity into said chamber around the periphery of said atomizing means at an angle to the plane of said atomizing disc whereby said atomized liquid feed is peripherally and radially discharged from said atomizing disc into said bond of gas; said gas inlet means being figured to deliver into said chamber said annular band of gas of sufficient thickness to prevent the atomized liquid feed from penetrating through said gas band and being positioned whereby said band of gas delivered into the chamber provides a zone of high turbulence in said chamber; means for supplying said liquid feed to said atomizing means; said atomizing means comprising a pair of spaced, collinear, rotary atomizers positioned adjacent opposite sides of said chamber, and whose common axis is concentric with the axis of said gas inlet means, and said gas inlet means comprises a pair of converging, opposed frustocones with their small bases respectively positioned around the periphery of each of said atomizers to provide a pair of inwardly directed converging annular gas streams which impinge in said chamber to form a zone of turbulence; means for exhausting gas from said chamber; means for removing concentrated liquid from said chamber.
 11. The apparatus of claim 10 wherein each of said gas inlet means are dimensioned to provide frustoconical inlet gas streams having a thickness of from about 1 1/2 inches to 7 inches at the periphery of said atomizer. 